[PATCH] watchdog: sunplus: fix sp_wdt_restart spin loop and timeout

[Guenter Roeck]

On Thu, Aug 20, 2026 at 02:53:04PM +0200, Andrew Gaylard wrote:
> sp_wdt_restart() returns immediately after writing WDT_RESUME. The
> kernel continues executing and the watchdog kthread could pet the
> watchdog before the short timeout expired, preventing reset.

Is this observed behavior or just an assumption ?

> 
> Add a spin loop so no other CPU can pet the watchdog while waiting for
> the reset. Set the restart timeout to ~1.5s.

I understand the first part, but why delay the reset by 1.5s ?
That is a functional change which needs an explanation.

Guenter

> 
> Signed-off-by: Andrew Gaylard <ag at ffroot.co.za>
> ---
>  drivers/watchdog/sunplus_wdt.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/watchdog/sunplus_wdt.c b/drivers/watchdog/sunplus_wdt.c
> index e5212f3d2e24..b44dcc307634 100644
> --- a/drivers/watchdog/sunplus_wdt.c
> +++ b/drivers/watchdog/sunplus_wdt.c
> @@ -61,10 +61,16 @@ static int sp_wdt_restart(struct watchdog_device *wdev,
>  
>  	writel(WDT_STOP, base + WDT_CTRL);
>  	writel(WDT_UNLOCK, base + WDT_CTRL);
> -	writel(0x0001, base + WDT_CNT);
> +	writel(0x20F5, base + WDT_CNT);	/* ~1.5s at 90kHz */
>  	writel(WDT_LOCK, base + WDT_CTRL);
>  	writel(WDT_RESUME, base + WDT_CTRL);
>  
> +	/* Spin until the watchdog resets us. This prevents any other CPU
> +	 * from petting the watchdog.
> +	 */
> +	while (1)
> +		cpu_relax();
> +
>  	return 0;
>  }
>  
> -- 
> 2.53.0
> 
>